I'm glad that everyone is so
concerned with both negative and positive IHC controls. There is certainly
more than one side to this issue. I will say that I don't think a positive QC
on every slide is absolutely necessary, for many reasons. If the QC is rare
& precious, then it is a waste of resources. As is running a negative
control for every possible technique permutation on small amounts of tumor. I
would rather have slides with tumor left for additional studies than have
wasted tumor sections on 4-6 negative controls. You can always evaluate
non-specific staining on slides that have had an antibody applied & that
are negative with that antibody. The CAP is specific that positive controls be
used for each antibody - see CAP checklist ANP.22550. They do not
specify for each slide. Since positive QC's should be kept filed for the same
number of years as the patient slide & records, it should be possible to
pull a QC slide from the IHC run for a particular slide. In the CAP comment on
ANP.22550, the use of internal QC's is also mentioned. Although there are many
ways of dealing with the issue of QC's, I'm sure we all want to do what is
prudent, abide by the regulations, and increase the level of patient care.
Just my 2 cents worth.

Patti LoykasekPhenopath
LaboratoriesSeattle, WA

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